ANALYSIS OF PREEMPTIVE LOSS PRIORITY-QUEUES WITH PREEMPTION DISTANCE

In a queueing system with preemptive loss priority discipline, custome rs disappear from the system immediately when their service is preempt ed by the arrival of another customer with higher priority. Such a sys tem can model a case in which old requests of low priority are not wor thy of deferred service. This paper is concerned with preemptive loss priority queues in which customers of each priority class arrive in a Poisson process and have general service time distribution. The strict preemption in the existing model is extended by allowing the preempti on distance parameter d such that arriving customers of only class 1 t hrough p - d can preempt the service of a customer of class p. We obta in closed-form expressions for the mean waiting time, sojourn time, an d queue size from their distributions for each class, together with nu merical examples. We also consider similar systems with server vacatio ns.